Irregular sleep patterns upend students’ natural body clocks and can leave them feeling jet-lagged, a condition that ultimately undermines their performance in the classroom, Dr. Charles Czeisler, one of the study’s authors, told CNN.

“When circadian rhythms are disrupted, it degrades many different physiological systems in the body and makes individuals much more vulnerable to adverse health outcomes,” said Czeisler, chief of the Division of Sleep and Circadian Disorders at Brigham and Woman’s Hospital in Boston. “That could be everything from catching a cold to gaining weight to diabetes, and here in this study, we’re showing it can degrade academic performance as well.”

The study followed 61 undergrads at Harvard College. The students reported on their sleep habits for 30 days using an online journal, and were then divided into two groups — those who followed a consistent sleep schedule and those who had different sleep patterns each day.

Researchers said there was no difference in the number of hours of sleep the students in each group got, just how they racked up their ZZZ’s. And by the end of the month, those students with regular sleep schedules reported higher GPAs.

More research is needed, but study authors say college students should know that sleep patterns could affect their academics.

That said, late bedtimes are OK — as long as students stick to a regular schedule, Czeisler noted.

“If you go to bed at 2 and get up at 9, that’s fine,” he told CNN. “You just have to consistently do the same thing.”